[PATCH] erofs-utils: Provide identical functionality without libuuid

[Norbert Lange <nolange79@gmail.com>]

The motivation is to have standalone (statically linked) erofs binaries
for simple initrd images, that are nevertheless able to (re)create
erofs images with a given UUID.

For this reason a few of libuuid functions have implementations added
directly in erofs-utils.
A header liberofs_uuid.h provides the new functions, which are
always available. A further sideeffect is that code can be simplified
which calls into this functionality.

The uuid_unparse function replacement is always a private
implementation and split into its own file, this further restricts
the (optional) dependency on libuuid only to the erofs-mkfs tool.

Signed-off-by: Norbert Lange <nolange79@gmail.com>
---
 dump/Makefile.am    |   2 +-
 dump/main.c         |   8 +---
 fsck/Makefile.am    |   2 +-
 lib/Makefile.am     |   4 +-
 lib/liberofs_uuid.h |   9 ++++
 lib/uuid.c          | 106 ++++++++++++++++++++++++++++++++++++++++++++
 lib/uuid_unparse.c  |  21 +++++++++
 mkfs/Makefile.am    |   6 +--
 mkfs/main.c         |  21 ++-------
 9 files changed, 149 insertions(+), 30 deletions(-)
 create mode 100644 lib/liberofs_uuid.h
 create mode 100644 lib/uuid.c
 create mode 100644 lib/uuid_unparse.c

diff --git a/dump/Makefile.am b/dump/Makefile.am
index c2bef6d..90227a5 100644
--- a/dump/Makefile.am
+++ b/dump/Makefile.am
@@ -7,4 +7,4 @@ AM_CPPFLAGS = ${libuuid_CFLAGS}
 dump_erofs_SOURCES = main.c
 dump_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
 dump_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
+	${liblz4_LIBS} ${liblzma_LIBS}
diff --git a/dump/main.c b/dump/main.c
index bc4e028..40af09f 100644
--- a/dump/main.c
+++ b/dump/main.c
@@ -17,10 +17,8 @@
 #include "erofs/compress.h"
 #include "erofs/fragments.h"
 #include "../lib/liberofs_private.h"
+#include "../lib/liberofs_uuid.h"
 
-#ifdef HAVE_LIBUUID
-#include <uuid.h>
-#endif
 
 struct erofsdump_cfg {
 	unsigned int totalshow;
@@ -620,9 +618,7 @@ static void erofsdump_show_superblock(void)
 		if (feat & feature_lists[i].flag)
 			fprintf(stdout, "%s ", feature_lists[i].name);
 	}
-#ifdef HAVE_LIBUUID
-	uuid_unparse_lower(sbi.uuid, uuid_str);
-#endif
+	erofs_uuid_unparse_lower(sbi.uuid, uuid_str);
 	fprintf(stdout, "\nFilesystem UUID:                              %s\n",
 			uuid_str);
 }
diff --git a/fsck/Makefile.am b/fsck/Makefile.am
index e6a1fb6..4176d86 100644
--- a/fsck/Makefile.am
+++ b/fsck/Makefile.am
@@ -7,4 +7,4 @@ AM_CPPFLAGS = ${libuuid_CFLAGS}
 fsck_erofs_SOURCES = main.c
 fsck_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
 fsck_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
+	${liblz4_LIBS} ${liblzma_LIBS}
diff --git a/lib/Makefile.am b/lib/Makefile.am
index faa7311..e243c1c 100644
--- a/lib/Makefile.am
+++ b/lib/Makefile.am
@@ -29,9 +29,9 @@ noinst_HEADERS += compressor.h
 liberofs_la_SOURCES = config.c io.c cache.c super.c inode.c xattr.c exclude.c \
 		      namei.c data.c compress.c compressor.c zmap.c decompress.c \
 		      compress_hints.c hashmap.c sha256.c blobchunk.c dir.c \
-		      fragments.c rb_tree.c dedupe.c
+		      fragments.c rb_tree.c dedupe.c uuid_unparse.c uuid.c
 
-liberofs_la_CFLAGS = -Wall -I$(top_srcdir)/include
+liberofs_la_CFLAGS = -Wall ${libuuid_CFLAGS} -I$(top_srcdir)/include
 if ENABLE_LZ4
 liberofs_la_CFLAGS += ${LZ4_CFLAGS}
 liberofs_la_SOURCES += compressor_lz4.c
diff --git a/lib/liberofs_uuid.h b/lib/liberofs_uuid.h
new file mode 100644
index 0000000..d156699
--- /dev/null
+++ b/lib/liberofs_uuid.h
@@ -0,0 +1,9 @@
+/* SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0 */
+#ifndef __EROFS_LIB_UUID_H
+#define __EROFS_LIB_UUID_H
+
+void erofs_uuid_generate(unsigned char *out);
+void erofs_uuid_unparse_lower(const unsigned char *buf, char *out);
+int erofs_uuid_parse(const char *in, unsigned char *uu);
+
+#endif
\ No newline at end of file
diff --git a/lib/uuid.c b/lib/uuid.c
new file mode 100644
index 0000000..acff81a
--- /dev/null
+++ b/lib/uuid.c
@@ -0,0 +1,106 @@
+// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
+/*
+ * Copyright (C) 2023 Norbert Lange <nolange79@gmail.com>
+ */
+
+#include <string.h>
+#include <errno.h>
+
+#include "erofs/config.h"
+#include "erofs/defs.h"
+#include "liberofs_uuid.h"
+
+#ifdef HAVE_LIBUUID
+#include <uuid.h>
+#else
+
+#include <stdlib.h>
+#include <sys/random.h>
+
+/* Flags to be used, will be modified if kernel does not support them */
+static unsigned erofs_grnd_flag = 
+#ifdef GRND_INSECURE
+    GRND_INSECURE;
+#else
+    0x0004;
+#endif
+
+static int s_getrandom(void *pUid, unsigned size, bool insecure)
+{
+    unsigned kflags = erofs_grnd_flag;
+    unsigned flags = insecure ? kflags : 0;
+
+    for (;;)
+    {
+        ssize_t r = getrandom(pUid, size, flags);
+        int err;
+        if (r == size)
+            break;
+        err = errno;
+        if (err != EINTR) {
+            if (err == EINVAL && kflags) {
+                // Kernel likely does not support GRND_INSECURE
+                erofs_grnd_flag = 0;
+                kflags = 0;
+                continue;
+            }
+            return -err;
+        }
+    }
+    return 0;
+}
+#endif
+
+void erofs_uuid_generate(unsigned char *pOut)
+{
+#ifdef HAVE_LIBUUID
+    uuid_t new_uuid;
+
+    do {
+        uuid_generate(new_uuid);
+    } while (uuid_is_null(new_uuid));
+#else
+    unsigned char new_uuid[16];
+    int res __maybe_unused;
+
+    res = s_getrandom(new_uuid, sizeof(new_uuid), true);
+    BUG_ON(res != 0);
+
+    // UID type + version bits
+    new_uuid[0] = (new_uuid[4 + 2] & 0x0f) | 0x40;
+    new_uuid[1] = (new_uuid[4 + 2 + 2] & 0x3f) | 0x80;
+#endif
+    memcpy(pOut, new_uuid, sizeof(new_uuid));
+}
+
+int erofs_uuid_parse(const char *in, unsigned char * uu) {
+#ifdef HAVE_LIBUUID
+    return uuid_parse((char *)in, uu);
+#else
+	unsigned char new_uuid[16];
+	unsigned hypens = ((1U << 3) | (1U << 5) | (1U << 7) | (1U << 9));
+    int i;
+
+	for (i = 0; i < sizeof(new_uuid); hypens >>= 1, i++)
+    {
+        char c[] = { in[0], in[1], '\0' };
+        char* endptr = c;
+        unsigned long val = strtoul(c, &endptr, 16);
+
+        if (endptr - c != 2)
+            return -EINVAL;
+
+        in += 2;
+
+        if ((hypens & 1U) != 0) {
+            if (*in++ != '-')
+                return -EINVAL;
+        }
+        new_uuid[i] = (unsigned char)val;
+    }
+    if (*in != '\0')
+        return -EINVAL;
+    memcpy(uu, new_uuid, sizeof(new_uuid));
+   	return 0;
+#endif
+}
\ No newline at end of file
diff --git a/lib/uuid_unparse.c b/lib/uuid_unparse.c
new file mode 100644
index 0000000..762a094
--- /dev/null
+++ b/lib/uuid_unparse.c
@@ -0,0 +1,21 @@
+// SPDX-License-Identifier: GPL-2.0+ OR Apache-2.0
+/*
+ * Copyright (C) 2023 Norbert Lange <nolange79@gmail.com>
+ */
+
+#include <stdio.h>
+
+#include "erofs/config.h"
+#include "liberofs_uuid.h"
+
+void erofs_uuid_unparse_lower(const unsigned char * buf, char *out) {
+	sprintf(out, "%04x%04x-%04x-%04x-%04x-%04x%04x%04x",
+			(buf[0] << 8) | buf[1],
+            (buf[2] << 8) | buf[3],
+			(buf[4] << 8) | buf[5],
+			(buf[6] << 8) | buf[7],
+			(buf[8] << 8) | buf[9],
+			(buf[10] << 8) | buf[11],
+			(buf[12] << 8) | buf[13],
+            (buf[14] << 8) | buf[15]);
+}
diff --git a/mkfs/Makefile.am b/mkfs/Makefile.am
index 709d9bf..a08dc53 100644
--- a/mkfs/Makefile.am
+++ b/mkfs/Makefile.am
@@ -2,8 +2,8 @@
 
 AUTOMAKE_OPTIONS = foreign
 bin_PROGRAMS     = mkfs.erofs
-AM_CPPFLAGS = ${libuuid_CFLAGS} ${libselinux_CFLAGS}
+AM_CPPFLAGS = ${libselinux_CFLAGS}
 mkfs_erofs_SOURCES = main.c
 mkfs_erofs_CFLAGS = -Wall -I$(top_srcdir)/include
-mkfs_erofs_LDADD = ${libuuid_LIBS} $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
-	${liblz4_LIBS} ${liblzma_LIBS}
+mkfs_erofs_LDADD = $(top_builddir)/lib/liberofs.la ${libselinux_LIBS} \
+	${libuuid_LIBS} ${liblz4_LIBS} ${liblzma_LIBS}
diff --git a/mkfs/main.c b/mkfs/main.c
index 94f51df..840222c 100644
--- a/mkfs/main.c
+++ b/mkfs/main.c
@@ -26,10 +26,7 @@
 #include "erofs/blobchunk.h"
 #include "erofs/fragments.h"
 #include "../lib/liberofs_private.h"
-
-#ifdef HAVE_LIBUUID
-#include <uuid.h>
-#endif
+#include "../lib/liberofs_uuid.h"
 
 #define EROFS_SUPER_END (EROFS_SUPER_OFFSET + sizeof(struct erofs_super_block))
 
@@ -90,9 +87,7 @@ static void usage(void)
 	      " -EX[,...]             X=extended options\n"
 	      " -L volume-label       set the volume label (maximum 16)\n"
 	      " -T#                   set a fixed UNIX timestamp # to all files\n"
-#ifdef HAVE_LIBUUID
 	      " -UX                   use a given filesystem UUID\n"
-#endif
 	      " --all-root            make all files owned by root\n"
 	      " --blobdev=X           specify an extra device X to store chunked data\n"
 	      " --chunksize=#         generate chunk-based files with #-byte chunks\n"
@@ -328,14 +323,12 @@ static int mkfs_parse_options_cfg(int argc, char *argv[])
 			}
 			cfg.c_timeinherit = TIMESTAMP_FIXED;
 			break;
-#ifdef HAVE_LIBUUID
 		case 'U':
-			if (uuid_parse(optarg, sbi.uuid)) {
+			if (erofs_uuid_parse(optarg, sbi.uuid)) {
 				erofs_err("invalid UUID %s", optarg);
 				return -EINVAL;
 			}
 			break;
-#endif
 		case 2:
 			opt = erofs_parse_exclude_path(optarg, false);
 			if (opt) {
@@ -626,11 +619,7 @@ static void erofs_mkfs_default_options(void)
 			     EROFS_FEATURE_COMPAT_MTIME;
 
 	/* generate a default uuid first */
-#ifdef HAVE_LIBUUID
-	do {
-		uuid_generate(sbi.uuid);
-	} while (uuid_is_null(sbi.uuid));
-#endif
+	erofs_uuid_generate(sbi.uuid);
 }
 
 /* https://reproducible-builds.org/specs/source-date-epoch/ for more details */
@@ -803,9 +792,7 @@ int main(int argc, char **argv)
 			  erofs_strerror(err));
 		goto exit;
 	}
-#ifdef HAVE_LIBUUID
-	uuid_unparse_lower(sbi.uuid, uuid_str);
-#endif
+	erofs_uuid_unparse_lower(sbi.uuid, uuid_str);
 	erofs_info("filesystem UUID: %s", uuid_str);
 
 	erofs_inode_manager_init();
-- 
2.39.2